<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div class="container">
        <header></header>
        <main></main>
        <footer></footer>
    </div>
   <!--  container --- display: flex; postion: relativer; flex-direction: column;
    header\footer --- flex-shrink:0
    main --- flex:1; flex-basis: auto; overflow: hidden; -->

</body>
<script src="./01.js"></script>
</html>